An Introduction to JS-Ctypes

[Andrea Giammarchi]

On Sun, Sep 18, 2011 at 6:19 AM, Brendan Eich <brendan at mozilla.com> wrote:

>
> Who ever said they didn't?
>

Sam did:
> You'd need a benchmark that shows that the object allocation you're
> avoiding here is worth the lack of flexibility.


I see what you are getting at now, but you're missing something: your test2
> has an object literal per loop iteration which cannot be optimized away
> easily. The object and array literals in my slide that you are concerned
> about:
>
>
>     - new Triangle([{ point: { x: 0, y: 0 },
>                          color: { r: 255, g: 255, b: 255 } },
>                        { point: { x: 5, y: 5 },
>                          color: { r: 128, g: 0, b: 0 } },
>                        { point: { x: 10, y: 0 },
>                          color: { r: 0, g: 0, b: 128 } }]);
>
> are neither mandatory -- see
> http://wiki.ecmascript.org/doku.php?id=harmony:binary_data_semantics#array_objectsand note how you can call new Triangle() and set members using dotted access
> and assignment -- nor as hard to optimize away than in the general case.
>

So you are suggesting to do something like this:

var p0 = new Point2D,
     p1 = new Point2D,
     p2 = new Point2D,
     c0 = new Color,
     c1 = new Color,
     c2 = new Color,
     px0 = new Pixel,
     px1 = new Pixel,
     px2 = new Pixel,
     t = new Triangle([px0, px1, px2])

and per each typed object assign properties ...

p0.x = 0; p0.y = 0;

... sure this avoid creation of literal but who's gonna do that ? OK, at
least it is possible.



>
> How did the performance change?
>


in my Mac 13ms VS 16ms surely more if I use the Atom based Netbook

Best Regards,
    Andrea Giammarchi
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